Columbium alloy



United States Patent 3,188,205 COLUMBIUM ALLOY Arthur B. Michael, Lake Forest, 111., assignor to Fansteel Metallurgical Corporation, Chicago, 111., a corporation of New York No Drawing. Filed Dec. 20, 1961, Ser. No. 160,943 8 Claims. (Cl. 75174) This application is a continuation-in-part of application Serial No. 824,783, filed July 3,1959, and now abandoned, which in turn is a continuation-in-part of application Serial No. 754,938, filed August 14, 1958, now abandoned. Said application Serial No. 754,938 is a continuation-inpart of Serial No. 674,211 filed July 25, 1957 and now issued as Patent No. 2,957,764, granted October 25, 1960.

The present invention relates to metal alloys or intermetallic compositions .and particularly to alloys and intermetallic compositions of columbium and tantalum.

There are described, in said Patent No. 2,957,764, binary alloys of columbium and tantalum which have high temperature oxidation resistance characteristics vastly superior to the corresponding characteristics of columbium and tantalum alone.

It was found that even though the oxidation rate of preferred binary alloys described in the aforementioned patent was as low as about of the oxidation rate of susbtantially pure columbium, the oxidation rate could be further improved and the high temperature strength of the alloy substantially increased. In accordance with this invention those characteristics and a number of other important physical characteristics have been vastly improved so as to provide the alloys with the attributes necessary fior use of the alloy in such articles as turbine blades and buckets, rocket nozzles and other devices to be utilized in high temperature and corrosive atmosphere environments.

The preferred embodiment of this invention which is more fully described hereinbelow, as an example of the improved physical characteristics, has a high temperature tensile strength which exceeds the high temperature tensile strength of substantially pure tungsten and has been tested at temperatures as high as about 3000 F. Further, alloys embodying this invention have exhibited excellent tabricability, weldability and low temperature ductility. Cold reductions, as by rolling and cold forging have been made up to 94% of the thickness of the material without intermediate anneal s.

Alloys embodying this invention are colum'bium and tantalum base alloys to which tungsten and/or molybdenum and zirconium and/or titanium have been added.

Within the scope of the invention, tantalum is present in the alloy in the range of from about 20% to about 35% by weight. (Throughout this specification and the claims appended hereto, the term percent and the symbol are used interchangeably to designate the proportion 'by weight of the particular designated constituent in and with respect to the total weight of the alloy, as those terms are ordinarily used to designate such proportions.)

When tungsten is present in the alloy alone, without molybdenum, it is present in the range of from about 5% to about 16%. When molybdenum is present in the alloy alone and without tungsten, it is present in the range of from about 3% to about When zirconium is used in the alloy alone and without titanium, it is present in the range of from about 0.3% to about 5%. When titanium is present in the alloy alone and without zirconium, it is present in the range of from about 0.2% to about 2%. a When tungsten and molybdenum are used together in the alloy, the mixture may be present in the range of from about 5% to about 16%, with a maximum of about 3,188,205 Patented June. 8, 1965 10% molybdenum.- Similarly, when zirconium and titanium are used together, the mixture may be present in the range of from about 0.3% to about 5%, with a maximum of about 2% titanium.

In addition to columbium and tantalum, tungsten and/ or molybdenum, and zirconium and/or titanium, the alloy preferably includes oxygen in the range of from about 0.01% to about 0.1%, and carbon in the rangeof from about 0.01% to about 0.1%.

The preferred ranges for the metallic constituents in alloys embodying this invention are from about 25% to about 30% tantalum, from about 8% to about 15% tungsten when used alone, from about 4% to about 10% molybdenum when used alone, from about 8% to about 15% tungsten and molybdenum with a maximum of about 10% molybdenum, and from 0.5% to 1.5% zirconium and/or titanium.

There are set forth below examples of alloys embodying this invention, results of tests of the alloys of the examples and exemplary procedures for making and testing the alloys. The examples are intended to be illustrative only and are not intended to place any limits or restrictions on the scope of the invention other than those other-wise described herein. it should be noted and understood that alloys embodying this invention m-ay be made An alloy or intermetallic composition of 60.54% co lumbium, 27.12% tantalum, 11.80% tungsten, 0.53% zirconium, 0.005% carbon, 0.002% oxygen and a minor quantity of impurities was prepared by electron beam melting a bar of the pressed and sintered metal powders of columbium, tantalum and tungsten in the specified proportions. The bar was beam melted twice to insure high purification and efiicient alloying of the metals. The beam melting was carried out in a vacuum of about 0.1 micron of mercury.

In general, in this and in the following examples, the tantalum material used had a starting purity of about 99.5% the columbium used had a starting purity of about 99.2%, the zirconium used had a starting purity of about 99.8%, the titanium used had a starting purity of about 99.8%, the tungsten used had a starting purity of about 99% and the molybdenum used had a starting purity of about 99%.

The double beam melted alloythen had the desired proportion of zinonium added thereto by tack welding a bar the proper quantity of zirconium thereon, after which the alloyed columbium, tantalum and tungsten was re melted with the zirconium by beam melting.

The initial metal powder bar was prepared by pressing a blend of powders of the metals at a pressure of about 50 tons per square inch to form a compact which was then sintered at a temperature of about 2000 C. and degassed for about 2 hours in a vacuum of about 1 to 2 microns. Initial pressing of the blended powders may be effected at pressures in the range of from about 20 to about 50 tons per square inch. Following pressing, the bar was sintered. Preferred sintering temperatures were in the range of from about 1600" C. to about 2000 C.

The beam melting procedure was carried out in an electron beam furnace of about 30 kva. The resulting alloy included carbon and oxygen in the small but important quantities designated above in this example. .After'completion of the preparation of the alloy, portions of it were subjected to various tests.

When tested for oxidation resistance in flowing air having a flow rate of about 1 charge per minute in a glow bar furnace, at 2000 F. for 16 hours, the alloy suffered 3 an oxidation penetration of about 0.01 cm. By comparison, substantially pure columbium subjected to the same oxidation test suffered a penetration of about 0.105

Indetermining the oxidation rate, i.e., penetration, the dimensions of the test article were measured prior to subjecting the same to the oxidation test conditions. The oxidation scale which formed on the surface of the article during testing was removed, as by grit blasting or grind ing, following which the thickness of the article was again measured. The change in dimensions provided the means of measuring the amount of metal lost by oxidation during the test period. The difference between the thickness of the original article and the thickness of the article following the exposure thereof to the oxidation test conditions is referred to herein as penetration.

This alloy was also tested for workability (cold reduction by rolling), tensile strength, creep rate and stress-torupture characteristics. It was found that the alloy could be cold rolled to more than a 90% reduction without intermediate anneals. It had a tensile strength of about 10,000 p.s.i. at 3000 F., and 22,500 p.s.i. at 2400 F. At 2000 F. and 17,000 p.s.i. the rupture time was greater than 158 hours. The secondary creep rate was only 3.6 inches/inch/hour at 20,000 p.s.i. at 2000 F.

Example II An alloy or intermetallic composition of about 62.6% columbium, 28.7% tantalum, 8% tungsten, 0.65% zirconium, 0.03% carbon, 0.03% oxygen and minor impurities was prepared by the procedure set forth in Example I. This alloy demonstrated improved characteristics when subjected to the same tests to which the alloy of Example I was subjected. For example, the alloy has a tensile strength of 10,400 p.s.i. at 2800 F., and 35,000 p.s.i. at 2200 F.

Example 111 An alloy or intermetallic composition of 63.2% columbium, 30.0% tantalum, 0.04% zirconium, and 6.4% tungsten was prepared by are melting an electrode of pressed and sintered powders of columbium, tantalum and zirconium having the specified proportions of constituents therein.

The electrode was prepared by pressing a blend of powders of the metals at a pressure of about 50 tons per square inch to form a compact which was then sintered at a temperature of about 2000 C. and degassed for about 2 hours in a vacuum of about 1 or 2 microns. Preferred sintering temperatures are in the range of from about 1600 C. to about 2000 C. and preferred pressing pressures are in the range of from about to about 50 tons per square inch. 7 Other conventional sintering conditions may be employed.

The arc melting procedure was carried out by melting the composite electrode with an are from a non-consumable electrode in an atmosphere of about 20 percent argon and about 80 percent helium. If desired, the protective atmosphere, which should be inert atmosphere, may be argon or helium or any other inert atmosphere that will not combine with the constituents of the alloy at elevated temperatures. If desired, the arc melting procedure may be effected in a vacuum.

The resulting arc melted alloy, when tested for oxidation resistance in flowing air having a flow rate of about 1 charge per minute in a glowbar furnace, and 2000 F. for 16 hours, had an oxidation penetration of about 0.015 cm. This compares favorably with an oxidation penetration of about 0.105 centimeter for substantially pure columbium under the same test conditions.

Further, the resulting arc melted alloy when tested for tensile strength in a stress to rupture test showed a stress for rupture of about 20,000 pounds per square inch in a test conducted for 100 hours at 2000 F. When substantially pure columbium is tested under the same test conditions, it shows a stress for rupture of about 13,000 pounds per square inch.

In determining the oxidation rate, i.e., penetration, the dimensions of the test article were determined prior to subjecting the sample to the oxidation test conditions. The oxidation scale which formed on the surface of the test article was removed, as by grit blasting or grinding, following which the thickness of the article was again measured. The change in dimensions provides the means of measuring the amount of metal lost by oxidation during the test period. The difference between the thickness of the original article and the thickness of the article following exposure to the oxidation test conditions is referred to herein as oxidation penetration.

Example IV An alloy or intermetallic composition of about 55.87% columbium, 31.42% tantalum, 0.56% zirconium, 7.99% tungsten and 4.17% molybdenum was prepared by the procedure set forth in Example III. That is, this alloy was prepared by pressing and sintering a blended mixture of metal powders in the proportions specified and are melting the sintered article in the manner set forth in Example III.

The resulting arc melted alloy, when tested for oxidation resistance in flowing air by subjecting the alloy to a temperature of 2000 F. in flowing air for a period of 16 hours, underwent an oxidation penetration of 0.014 cm. The hour stress for rupture at 2000 F. was 21,000 pounds per square inch.

These results compare very favorably with an oxidation penetration of 0.105 cm. and a 100 hour stress for rupture at 2000 F. of 13,000 pounds per square inch for substantially pure columbium subjected to the same test conditions.

Example V An alloy or intermetallic composition of about 55.86% columbium, 31.52% tantalum, 8.02% tungsten, 4.18% molybdenum and 0.42% titanium was prepared by the procedure set forth in Example III. That is, this alloy was prepared by pressing and sintering a blended mixture of metal powders in the proportions specified and are melting the sintered article in the manner set forth in Example III.

The resulting arc melted alloy, when tested for oxidation resistance in flowing air by subjecting the alloy to a temperature of 2000 F. in flowing air for a period of 16 hours, underwent an oxidation penetration of 0.014 cm. The 100 hour stress for rupture at 2000 F. was 21,000 pounds per square inch.

These results compare very favorably with an oxidation penetration of 0.105 cm. and a 100 hour stress for rupture at 2000 F. of 13,000 pounds per square inch for substantially pure columbium subjected to the same test conditions. 7

Example VI An alloy or intermetallic composition of about 55.50% columbium, 31.50% tantalum, 0.48% zirconium, 8.01% tungsten, 4.18% molybdenum and 0.33% titanium was prepared by the procedure set forth in Example III. That is, this alloy was preparedby pressing and sintering a blended mixture of metal powders in the proportions specified and arc melting the sintered article in the manner set forth in Example III.

The resulting arc melted alloy, when tested for oxidation resistance in flowing air by subjecting the alloy to a temperature of 2000 F. in flowing air for a period of 16 hours, underwent an oxidation penetration of 0.014 cm. The 100 hour stress for rupture at 2000 F. was 21,500 pounds per square inch.

These results compare very favorably with an oxidation penetration of 0.105 cm. and a 100 hour stress for rupture at 2000 F. of 13,000 pounds per square inch for substantially pure columbium subjected to the same test conditions.

It should be understood that numerous modifications and variations may be effected Without departing from the true spirit and scope of the novel concepts and principles of this invention. The foregoing detailed description of the invention and embodiments thereof is given for clearness and for understanding of the invention, and no unnecessary limitations should be understood or implied therefrom, since some modifications will be obvious to those skilled in the art.

I claim:

1. A columbium-tantalum base alloy having high resistance to oxidation and high strength at elevated temperatures, consisting essentially of from about 20% to about 35% tantalum, a member selected from the group consisting of tungsten and molybdenum and mixtures thereof, the tungsten when selected being in the range of from about to about 16%, the molybdenum when selected being in the range of from about 3% to about the mixture when selected being in the range of from about 5% to about 16% with up to about 10% molybdenum, a member selected from the group consisting of zirconium and titanium and mixtures thereof, the zirconium when selected being in the range of from about 0.3% to about 5%, titanium when selected being in the range of from about 0.2% to about 2%, the mixtures thereof when selected being in the range of from about 0.3% to about 5% with up to about 2% titanium, and the balance being substantially all columbium.

2. A columbium-tantalum base alloy having high resistance to oxidation and high strength at elevated temperatures, consisting essentially of from about 25% to about 30% tantalum, a member selected from the group consisting of tungsten and molybdenum and mixtures thereof, the tungsten when selected being in the range of from about 8% to about the molybdenum when selected being in the range of from about 4% to about 10%, the mixture when selected being in the range of from about 8% to about 15% with up to about 10% molybdenum, a member selected from the group consisting of zirconium and titanium and mixtures thereof, the zirconium when selected being in the range of from about 0.5% to about 1.5%, the titanium when selected being in the range of from about 0.5% to about 1.5%, the mixtures thereof when selected being in the range of from about 0.5 to about 1.5%, and the balance being substantially all columbium.

3. A columbium-tantalum base alloy having high resistance to oxidation and high strength at elevated temperatures, consisting essentially of from about 25% to about 30 tantalum, a member selected from the group consisting of tungsten and molybdenum and mixtures thereof, the tungsten when selected being in the range of from about 8% to about 15% and the molybdenum when selected being in the range of from about 4% to about 10%,

the mixture when selected being in the range of from about 8% to about 15% with up to about 10% molybdenum, a member selected from the group consisting of zirconium and titanium and mixtures thereof, the zirconium when selected being in the range of from about 0.5 to about 1.5 the titanium when selected being in the range of from about 0.5% to about 1.5 the mixtures thereof when selected being in the range of from about 0.5% to about 1.5%, and the balance being substantially all columbium with oxygen in the range of from about 0.001% to about 0.1% and carbon in the range of from about 0.001% to about 0.1%.

4. A columbium-tantalum base alloy having high resistance to oxidation and high strength at elevated temperatures, consisting essentially of about 62.6% columbium, about 28.7% tantalum, about 8% tungsten and about 0.65% zirconium.

5. A columbium-tantalum base alloy having high resistance to oxidation and high strength at elevated temperatures, consisting essentially of about 62.6% columbium, about 28.7% tantalum, about 8% tungsten, about 0.65% zirconium, about 0.03% carbon and about 0.03% oxygen.

6. A columbium-tantalum base alloy consisting essentially of about 60.5% columbium, about 27% tantalum, about 11.8% tugnsten and about 0.5 zirconium.

7. A columbium-tantalum base alloy consisting essentially of about 60.5 columbium, about 27% tantalum, about 11.8% tungsten, about 0.5% zirconium, about 0.005% carbon and about 0.002% oxygen.

8. A columbium-tantalum base alloy having resistance to oxidation and high strength at elevated temperatures, consisting essentially of from about 25% to about 30% tantalum, from about 8% to about 15% tungsten, from about 0.5% to about 1.5% zirconium, and the balance being substantially all columbium with oxygen in the range of from about 0.001% to about 0.1% and carbon in the range from about 0.001% to about 0.1%.

References Cited by the Examiner UNITED STATES PATENTS 1,588,518 6/26 Brace -174 2,187,630 1/40 Schafer 75-174 2,198,914 4/40 Leemans 75-174 2,822,268 2/58 Hix 75-174 2,838,396 6/58 Rhodin 75-174 2,860,970 11/58 Thielemann 75-174 2,883,282 4/59 Wainer 75-174 2,907,654 10/ 59 Thielemann 75-174 2,939,785 6/60 Weatherly 75-174 2,973,261 2/61 Frank 75-174 3,115,407 12/63 Hum 75-174 DAVID L. RECK, Primary Examiner.

RAY K. WINDHAM, WINSTON A. DOUGLAS,

Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,188,205 June 8, 1965 Arthur B. Michael It is hereby certified that error appears in the above numbered patent reqliring correction and that the said Letters Patent should read as correctedbelow.

Column 2, lines 8 and 9, for "0.01%", each occurrence,

read 0.001%

Signed and sealed this 26th day of October 1965.

SEAL) ttest:

EDWARD J. BRENNER Commissioner of Patents RNEST W. SWIDER Hosting Officer 

1. A COLUMBIUM-TANTALUM BASE ALLOY HAVING HIGH RESISTANCE TO OXIDATION AND HIGH STRENGTH AT ELEVATED TEMPERATURES, CONSISTING ESSENTIALLY OF FROM ABOUT 20% TO ABOUT 35% TANTALUM, A MEMBER SELECTED FROM THE GROUP CONSISTING OF TUNGSTEN AND MOLYBDENUM AND MIXTURES THEREOF, THE TUNGSTEN WHEN SELECTED BEING IN THE RANGE OF FROM ABOUT 5 TO ABOUT 16%, THE MOLYBDENUM WHEN SELECTED BEING IN THE RANGES OF FROM ABOUT 3% TO ABOUT 10%, THE MIXTURE WHEN SELECTED BEING IN THE RANGE OF FROM ABOUT 5% TO ABOUT 16% WITH UP TO ABOUT 10% MOLYBEDENUM, A MEMBER SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM AND TITANIUM AND MIXTURES THEREOF, THE ZIRCONIUM WHEN SELECTED BEING IN THE RANGE OF FROM ABOUT 0.3% TO ABOUT 5%, TITANIUM WHEN SELECTED BEING IN THE RANGE OF FROM ABOUT 0.2% TO ABOUT 2%, THE MIXTURES THEREOF WHEN SELECTED BEING IN THE RANGE OF FROM ABOUT 0.3% TO ABOUT 5% WITH UP TO ABOUT 2% TITANIUM, AND THE BALANCE BEING SUBSTANTIALLY ALL COLUMBIUM. 